use document.createElement instead of html string, fixes #336
outerHTML as utility method
use document.createElement in result_add_group for consistency
Merge branch 'dom-create-element' of github.com:koenpunt/chosen into koenpunt-dom-create-element
Move outerHTML into Chosen's Abstract class until we find it a
permanent home with other dom utilities.
Merge pull request #1430 from harvesthq/koenpunt-dom-create-element

Use document.createElement instead of html string